The present invention relates generally to manipulators, and more particularly concerns a manipulator having a rotational mount capable of operating in ultra-high vacuum at either very high or very low temperatures. The invention will be specifically described in connection with a manipulator for cryogenically cooling a rotatable test specimen about a highly thermally conductive rotary joint movable in three mutually perpendicular directions within an ultra-high vacuum chamber.
Scientific tests and analyses of particular material specimens are best conducted at extreme temperatures under ultra-high vacuum conditions. Hence, it is necessary to conduct many of these tests in an ultra-high vacuum chamber. In many of these tests, it is highly desirable to change both the position and orientation of the test specimen within the vacuum chamber. Manipulation of the test specimen is particularly important where more than one type of surface analytical probe is utilized in the testing, as it allows the specimen to be moved to different positions for different analyses. Typical tests and analyses on material samples in this category include Auger analysis, x-ray photoelectron spectroscopy, thermal desorption spectroscopy and argon ion sputter cleaning. Furthermore, many of these tests require that the test specimen be constantly maintained at cryogenic temperature levels.
One method of maintaining a test specimen at a constant extremely low cryogenic temperature involves continuously cooling by a thermal media, such as liquid helium or liquid nitrogen. The thermal media is applied to the test specimen from a pressurized dewar through a transfer line or other piping arrangement. When the tests are performed in an ultra-high vacuum chamber, practical necessity dictates that the dewar be located outside the chamber, and that the media be piped through a sealed opening in the chamber wall. The need to seal the piping arrangement entering the ultra-high vacuum chamber conflicts with the need to supply thermal media to the test specimen when the test specimen is moved within the vacuum chamber.
A proposed arrangement for accommodating both of these conflicting needs involves supplying the thermal media to the test specimen through a relatively small (in diameter) helically wound concentric pipe arrangement. The concentric pipe arrangement is fixedly sealed as it enters the vacuum chamber. However, the discharge end of the pipe arrangement is movable within a limited range along with the test specimen. This concentric pipe arrangement resembles a helically wound spring and accommodates limited rotational movement of the test specimen. The requirement for the pipe size to be relatively small in diameter presents significant thermal conductance limitations. Moreover, this arrangement will not accommodate a full 360.degree. of test specimen rotation.